What do YOU use back testing for?

I have been trying to build skills being a day trader or scalper, so I've just been paper trading to test my strategies. Should I look into back testing?

What back testing softwares are the easiest, but most powerful to use? Do most of you program your strategies in a software and then execute those strategies in a different platform? Or is your platform integrated for back testing and then automated order executions?

I have been trying to build skills being a day trader or scalper, so I've just been paper trading to test my strategies. Should I look into back testing?

What back testing softwares are the easiest, but most powerful to use? Do most of you program your strategies in a software and then execute those strategies in a different platform? Or is your platform integrated for back testing and then automated order executions?